<!DOCTYPE html>

<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Title</title>

        <style>
            *{
                margin:0;
                padding: 0;
            }
            .back-img{
                width: 100%;
                height: 750px;
                background-image: url("home.jpg");
                background-size: cover;
                overflow: hidden;
            }
            .test{
                position: relative;
                background: gray;
                width: 500px;
                height: 200px;
                margin: 50px auto;
            }
        </style>

    </head>

    <body>

    <div class="back-img">
        <div class="test"></div>
    </div>

    </body>

</html>